The Shadow Out of Time

The Shadow Out of Time begins, like many of his best tales, with a man experiencing or discovering something that irrevocably alters the fabric of his life, sending him scrambling to restore his sanity; but in this case this aspect is reduced to little more than a framing device for detailed descriptions of how the Great Race – an effectively disembodied race that successively inhabits the bodies of others throughout the universe – manages incredible feats of time and space travel, and of descriptions of the ruined habitations of the Old Ones in a desert in Australia. (Goodreads)